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Zer0-X
Account closed
Registered: Aug 2008
Posts: 78 |
VSP crash (not solved yet)
I recently found my C64C to be very prone to crash with certain demos and finally managed to create a reproducible crash while banging the $d011 register so I hooked up my logic analyzer and here are some logs of the event taking place.
http://oms.wmhost.com/misc/VSP_Crash_100MHz.zip
A testprogram was looped at address $0ff0. It could've been placed at pretty much any $xxf0 address and it still would crash within few seconds. Running the code at lower offset on the memorypage quite effectively prevented it from crashing on the machine used for testing. A shorter version with only inc/dec/inc/jmp not crossing the page boundary crashes.
The symptoms were always the same; low address byte of the 2nd inc at $xxf7 and/or the opcode of the jmp at $xxff are suddenly trashed. The byte at $xxf7 ends up being 0x00, 0x01, 0x10 or 0x1d. Byte at $xxff ends up being 0x0c, 0x40, 0x48 or 0x4d.
As a post-work the decoupling caps of the memorychips in the C64C used were replaced and a new thick wire delivering power directly to the memorychips was soldered in place. This had no effect and the machine still crashes with this code, as well as with Booze Design demos Royal Arte and Tsunami for example. Powersupply used is a C128 PSU with C64 powercable soldered next to the C128 powercable.
Logfiles VSP Crash 100MHz 3_31.csv/txt have the actual crash event taking place.
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enthusi
Registered: May 2004
Posts: 677 |
Personally, I think VSP-fx should be depreciated for that very reason. And yes, I know that's alot to ask.
But I think that's what kept the c64-scene that vivid.
Now, with it becoming more and more of an emulator scene (much less so than any other oldschool systems though to my knowledge) VSP crashes may become less and less relevant but I think its an important principle to at least remember this.
Same goes for grey dots, samples on new sid, audio-screen-sync timed to emulator-delays etc.
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DeeKay
Registered: Nov 2002
Posts: 363 |
n2c: that's really too much to ask! <:-) I for one wouldn't wanna miss Dutch Breeze 's diagonal scrolling logo or amazing dragon-intro, Gotcha's awesome AGSP-gfx in That's Design , Thomas Heinrich's amazing GFX in Another World , Mayhem in Monsterland and countless amazing bitmap scrolling fonts for anything in the world!
It's the only known way to actually scroll bitmap further than 7 pixels, that's why VSP has been used extensively throughout the c64's software catalogue ever since it was discovered (somewhen in the late 80s IIRC), and asking people NOW to stop using it is like asking them to stop using sprites!...
No, we must come up with a hardware fix - and if we can't, well, it'll just have to go on like it did before... which wasn't really THAT annoying, tbh I never had a single machine where VSPs crashed! <:-) And I've owned a few!... |
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encore
Registered: Aug 2010
Posts: 67 |
Quoting SkateDon't we have a contact with any ex-Commodore engineers? If i were one of them and someone asked me a question like VSP bug, I'd be interested in finding the cause of the problem. I'm not saying they would be interested or they could help but why not inviting them to this discussion?
I agree and wrote a suggestion in the start of this thread:
Quoting encoreHow about asking Bil Herd? After seeing a couple of his videos, I could imagine that he would have an idea or two.
http://c128.com/forums/general-discussion
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Skate
Registered: Jul 2003
Posts: 494 |
@encore: i wish i knew who Bil Herd was. :))) so, anyone contacted or planning to contact him?
edit: i sent a message to Jeri Ellsworth to join and/or invite Bil Herd and others to this discussion. i just remembered even if i don't have a contact with the guys, i have a contact with someone who has a contact with them. :) |
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Shadow
Account closed
Registered: Apr 2002
Posts: 355 |
I'm not enough of a hardware guru to understand all the intricacies of this discussion, but at least it seems to me that the hardware "bug" is confirmed, and it would be good if it would convince people to stop using the god damn VSP effects!
I got a bit annoyed when I sat down to watch the x2012 demos and had to resort to an emulator to watch Trick and treat because it crashed on the VSP effect on the first disc.
I don't see why there is such a large acceptance of VSP when it is not working properly for a large percentage of the hardware. It would be like releasing a demo with an IRQ loader that only runs on 1541-II (and not 1541-I, oceanic, 1541U etc.) or something. Sure it works for those that have that hardware, and you can tell those that don't to "just buy one", but people would rightfully think that your code is a bit crappy.
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ready.
Registered: Feb 2003
Posts: 441 |
Or forsee a way to skipp the VSP part so the demo can continue. This is the best compromise in my opinion. Without VSP lots of nice effects would be trashed, but adding a way to keep compatibility is also nice. |
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Oswald
Registered: Apr 2002
Posts: 5086 |
 http://www.quickmeme.com/meme/3rp4cj
VSP is accepted since before dutch breeze or so, and it is even more so since emulators, get a machine which can handle it. |
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chatGPZ
Registered: Dec 2001
Posts: 11359 |
Quote:I don't see why there is such a large acceptance of VSP when it is not working properly for a large percentage of the hardware. It would be like releasing a demo with an IRQ loader that only runs on 1541-II (and not 1541-I, oceanic, 1541U etc.) or something. Sure it works for those that have that hardware, and you can tell those that don't to "just buy one", but people would rightfully think that your code is a bit crappy.
don't ever diss dutch breeze, lamer.
=P |
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lft
Registered: Jul 2007
Posts: 369 |
Remember that the VSP crash could occur even when we don't deliberately try to use VSP. For instance, consider a very simple up-scrolling game that does everything by the book and doesn't even have a raster interrupt. It would still have to change YSCROLL from 3 to 0 during initialisation, and if this happens during the visible portion of rasterline $30 (and there's a 0.2% probability of this), it could trigger a VSP crash. So it is a real bug (in the sense that specifications are violated) that some machines have. Do we fix those machines or do we avoid changing YSCROLL? |
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raven
Account closed
Registered: Jan 2002
Posts: 137 |
Shadow: You'll be surprised how many demos don't work on my 128D due to loaders that don't like the 1571 drive.
A few recent examples are "Trick and Treat" and "Edge of Disgrace".
With other demos there are random crashes after file loading ("Artphosis" and "Vicious SID 2" are such examples).
As for VSP, since the 80's I owned or had access to over 50 different C64 and C128/D machines.
I still haven't found a machine that would crash with VSP and I tried really hard to find one back when testing "Insomnia", which uses VSP quite heavily.
My only assumption is that these machines are rare, which is why I don't think VSP should be "banned" :)
I agree with Oswald, get a machine that can handle it ;) |
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